Background and aim: Today, increasing usage of microwaves generator sets such as cell phones, have been caused much worry related to their waves effects on human health. In this research, simulated waves effects of cell phones with frequency of 940MHz have been studied on hematopoiesis system of Balb/C mouse embryo. Methods: In an experimental study pregnant mice (Balb/C) were used as a laboratory model. The mice were divided into control, sham-exposed and experimental groups. The experimental groups were exposed to the waves on the 8th day of embryonic development for 4 or 10 days (everyday for 4 hours). At the end of treatment period, the experimental samples, sham-exposed and control related to morphology and histology studies of hematopoiesis organs were done by light microscope. Using t-test and Mann-Whitney test, the quantitative data were analyzed. Results: Morphologic study of embryos which were 18 days old didn’t show any abnormality but the weight of experimental embryos (1.263±0.017 gr) compared with sham-exposed (1.268±0.006 gr) showed significant increase (P<0.05). The study of tissue sections in embryos which were 12 days old didn’t show significant change in tissue and cellular position of yolk sac of experimental samples as compared with control group. Also, tissue studies of embryos which were 18 days old didn’t show any changes in general structure of liver, spleen, marrow bone but the number of Megakaryocytes of spleen and erythrocytes which had not nucleus in bone marrow of experimental samples showed significant increase as compared with the sham-exposed. The number of erythrocytes in liver which had not nucleus also showed significant increase as compared with the sham-exposed (P<0.05). Conclusion: Waves of cell phones with frequency of 940MHz don’t affect on general structure of liver, spleen, bone marrow of Balb/C embryos but it causes significant changes in the number of cells of these tissues.